It was "unwise" for President Donald Trump to question intelligence reports concerning Russian meddling in the 2016 election while speaking during a joint press conference Thursday, former Ambassador Nicholas Burns said.

"The U.S. intelligence community is rarely united on any issue," Burns, now a professor of diplomacy and international relations at Harvard's Kennedy School of Government, commented during a CNN "New Day" panel discussion. "They've been united for six months on this issue in their public report to the American people."

Trump's comments came during a joint news conference with Polish President Andrzej Duda in Poland on Thursday, where Trump opened his second visit to Europe. The trip next takes him to Germany for the G-20 summit, where he will meet with Russian President Vladimir Putin.

The president's comments also were not wise politically, said Burns, as the Senate voted just two weeks ago, by a 97-2 vote, to impose new sanctions on Russia. That effort was led by Senate Republicans, Burns pointed out.

"He's out of step with his own political party," the former ambassador said.

Trump also "is not defending the United States," said Burns, and that is one of the basic duties of a president.

"Russia launched a cyberattack on the American election," said Burns. "They got into the databases of 21 American states ... he gave a gift to Putin here on the eve of their meeting."

Instead, Putin needs to learn there will be repercussions and tangible steps by the United States to penalize Russia for its actions, Burns said.

"If you don't do that, think about what Putin might do to our 2018 midterms or the 2020 presidential election," said Burns. "I think it's dereliction of a basic duty of the president to defend the United States. He's out of step with the rest of the country. Very unwise to say what he did this morning."

Burns, also appearing on MSNBC Thursday, said Trump is planning to meet with South Korea President Moon Jae-In and Prime Minister Shinzo Abe of Japan, and he is right to meet with the two countries, as they are treaty allies of the United States.

"It is good to start with this," he said. "It also makes sense for the three countries to coordinate on our strategy because clearly the Chinese are not going to help strategically" with North Korea ... hopefully the Europeans will be able to help push on the Chinese and Russians to be much more critical of the North Korean ballistic missile test this week."

It was "unwise" for President Donald Trump to question intelligence reports concerning Russian meddling in the 2016 election while speaking during a joint press conference Thursday, former Ambassador Nicholas Burns said.